From 37bd2fb7d7bc3e38e132d390826790a0b91c6fe4 Mon Sep 17 00:00:00 2001
From: Leo Singer <leo.singer@ligo.org>
Date: Wed, 29 Apr 2020 11:32:01 -0400
Subject: [PATCH] Speed up import by replacing pkg_resources with
 importlib.resources

Speed up `import ligo.skymap` by up to a second by replacing uses of
`pkg_resources` with the new Python standard library module
`importlib.resources` (or, for Python < 3.7, the backport
`importlib_resources`). The old `pkg_resources` module is known to be
slow because it does a lot of work on startup.

See, for example,
[pypa/setuptools#926](https://github.com/pypa/setuptools/issues/926) and
[pypa/setuptools#510](https://github.com/pypa/setuptools/issues/510).
---
 CHANGES.rst              | 8 +++++++-
 ligo/skymap/plot/cmap.py | 9 +++++++--
 setup.cfg                | 1 +
 3 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/CHANGES.rst b/CHANGES.rst
index 93b62061..f663e120 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -5,7 +5,13 @@ Changelog
 0.2.1 (unreleased)
 ==================
 
-- No changes yet.
+- Speed up ``import ligo.skymap`` by up to a second by replacing uses of
+  ``pkg_resources`` with the new Python standard library module
+  ``importlib.resources`` (or, for Python < 3.7, the backport
+  ``importlib_resources``). The old ``pkg_resources`` module is known to be
+  slow because it does a lot of work on startup. (See, for example,
+  https://github.com/pypa/setuptools/issues/926 and
+  https://github.com/pypa/setuptools/issues/510.)
 
 0.2.0 (2020-04-21)
 ==================
diff --git a/ligo/skymap/plot/cmap.py b/ligo/skymap/plot/cmap.py
index 3dacf5c3..893f4595 100644
--- a/ligo/skymap/plot/cmap.py
+++ b/ligo/skymap/plot/cmap.py
@@ -16,17 +16,22 @@
 #
 """Register some extra Matplotlib color maps"""
 
+try:
+    from importlib import resources
+except ImportError:
+    # FIXME: remove after dropping support for Python < 3.7
+    import importlib_resources as resources
+
 from matplotlib import cm
 from matplotlib import colors
 import numpy as np
-import pkg_resources
 
 __all__ = ()
 
 
 for name in ['cylon']:
     # Read in color map RGB data.
-    with pkg_resources.resource_stream(__name__, name + '.csv') as f:
+    with resources.open_text(__package__, name + '.csv') as f:
         data = np.loadtxt(f, delimiter=',')
 
     # Create color map.
diff --git a/setup.cfg b/setup.cfg
index 69151c8e..42ece754 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -42,6 +42,7 @@ install_requires =
     astropy-healpix>=0.3  # https://github.com/astropy/astropy-healpix/pull/106
     healpy
     h5py
+    importlib-resources;python_version<'3.7'
     lalsuite>=6.53
     lscsoft-glue>=2.0.0
     ligo-gracedb>=2.0.1